Minutes for Compton Review Meeting on July 21, 2009

Present: D. Dale, D. Sober, Rory, Stanley, Aron, Maggie, Victor, Pawel, Yelena, Dmitry, Ilya, Ashot, Liping, Mahbub, Mark

(1) Comments to Yelena's Compton presentation:
   (a) For forward production, the reconstructed z vertex may not be the optimized kinematic parameter to extract  the
      yield, particularly for 12C target where the z resolution is largely smeared by multiple scattering in 
      the target.
   (b) The cross section result for low energy region needs more work. One needs better understanding of
       the detector responces at this energies (HyCal trigger efficiency and tagger).
   (c) The Tagging ratio stability is over estimated by using the entire period of pi0 data taking process. 
       It should be estimated within one Compton running  period only.
   (d) The differentioal cross sections are needed for the publication.      

(2) Comments to Pawel's Compton   presentation:
    (a) Recommend to finish differential cross section (other than differential cross sections in the HyCal solid angle).
    (b) recommended to have the same for the beryllium target.

(3)  Comments to Ilya's Compton presentation: 
    (a) Suggested to try other kinematic parameter other than z vertex for the yield extraction.
    (b) Recommended to have diff. cross sections.
    

(4) Ilya gave a presentation on new pi0 analysis with unconstrained method. His new result for the  
    pi0 decay width is 7.72+/-0.19 eV which agrees to his previous constrained result of 7.67 eV. 
    (a) It was suggested that both groups double check the theoretical modeles used in the fit.  
    (b) Dustin needs to improve his statistics in his theoretical distributions. 
    (c) Both groups are reminded our previous desicion to cross check the fitting before the publication.

(5) General discussion on how to finish and publish the Compton results:
    (a) We need to publish the Compton results by the end of this summer.
    (b) We will include in this publication only the higher energy ( ~5 GeV) part only. The low energy part will
        be sent for publication separately after finishing the requested additional analysis for that region.
    (c) The publication should include: (1) the total cross section; (2)the differential  cross sections for several 
        forward angles and/or (3) the differential cross section at the HyCal (crystal) solid angles. These has to 
        be done for 12C and for Be if statistics is enough. 
    (d) Each group should provide three plots for each target with an updated analysis note by the end of August.
    (e) The Committee for the Compton paper includes: Pawel, Yelana, Ilya, Liping (chair) and Ashot. 
    (f) Liping will draft the Compton paper by the end of August.
    (g) Special meetings will be arranged later in next weeks to discuss how to extract the differential cross section
        (if needed).